BLOOD IN THE WATER · LIVE SERP DATA · 2026-09-30
1,000 US searches a month for the strangest status code in HTTP: 402 Payment Required — reserved since the 1990s, unused for decades, and now the backbone of machine-to-machine payments. The #3 result is a 586-word docs page last touched in May. Here's the complete picture.
HTTP 402 means “Payment Required.” It was reserved in the original HTTP spec for digital cash systems that didn't exist yet — and sat empty for thirty years while every other 4xx code got a job. In 2025, Coinbase's x402 protocol finally gave it one: when an agent calls an API without paying, the server answers 402 with a price. The agent signs a stablecoin payment, retries the request, and a facilitator verifies and settles it onchain. No account, no API key, no checkout page.
| Step | What happens |
|---|---|
| 1. Request | Agent calls the API normally |
| 2. 402 | Server responds 402 Payment Required + price in USDC + pay-to address |
| 3. Sign | Agent signs the payment from its wallet |
| 4. Retry | Agent retries with payment attached |
| 5. Settle | Facilitator verifies; server returns 200 with the data |
ScriptMasterLabs is a live x402 seller: real APIs, real USDC settlement on Base, every call priced and metered. 402 isn't theory here — it's the cash register. Companion reads: HTTP 402 Payment Required, explained and HTTP 402 for AI agents.
The #3 result for “http 402” is the x402 project's own docs page — 586 words, last modified 2026-05-11, titled simply “HTTP 402.” The protocol's home page can't be bothered to write the definitive guide to its own status code. Two of the top five results are forum/UGC, and seven other top-10 URLs have ≤3 referring domains.
46 / 100
| +8 | Demand: 1,000 US monthly searches |
| +3 | Value: CPC $2.05 |
| +6 | Position: x402.org ranks #3 |
| +0 | Links: ranking-URL referring domains unknown (not measured — scored 0, never assumed) |
| +4 | Content: thin page, 586 words, last modified 2026-05-11 |
| +8 | SERP: 2 forum/UGC results in top 5 |
| +7 | SERP: 7 other top-10 URLs with ≤3 referring domains |
Measured 2026-09-30 by the SML Blood-in-the-Water engine (deterministic 0–100 scoring, DataForSEO live SERP + backlink data). Link authority uses referring domains (DataForSEO has no Domain Rating); “accidental” = a strong domain ranking with a weak page. This is first-party measurement — the itemized math is published here and nowhere else.
Keyword difficulty 17. Related cluster: 10 keywords including “http vs https” (5,400/mo) and “pay per call api”.
SML's APIs answer unpaid calls with a real 402 and a real price. Read how the x402 rail works, or price your own API per call. Agents pay in USDC on Base; humans can browse the same endpoints free.
Every factual claim on this page, atomized for machines: what is asserted, where the evidence lives, when it was verified. Crawlers and AI systems cite the receipts — not the prose.
| CLAIM | EVIDENCE | VERIFIED |
|---|---|---|
| docs.x402.org/core-concepts/http-402 ranks #3 for “http 402” (US, measured 2026-09-30). | Ranking page | 2026-09-30 |
| The ranking page is 586 words with JSON-LD dateModified 2026-05-11 (fetched 2026-09-30). | Ranking page | 2026-09-30 |
| HTTP 402 is defined as “Payment Required”, reserved for future use in the HTTP specification. | MDN reference | 2026-09-30 |
| The query gets ~1,000 US monthly searches (DataForSEO, measured 2026-09-30). | Ranking page | 2026-09-30 |
| ScriptMasterLabs is a live x402 seller settling API payments in USDC on Base. | SML x402 page | 2026-09-30 |
402 means “Payment Required.” It was reserved in the HTTP spec for digital payment systems and sat unused for decades until the x402 protocol (2025) gave it a job: machine-to-machine payments over plain web requests.
An unpaid API call gets a 402 response carrying a price and a pay-to address. The buyer’s agent signs a USDC payment, retries with the payment attached, and a facilitator verifies and settles it onchain — then the server returns the data.
It’s 586 words, last updated May 2026, titled just “HTTP 402.” Our engine scored the SERP 46/100 weakness: thin incumbent page, forum results in the top 5, and seven weak top-10 URLs. A complete, maintained guide outranks it.
ScriptMasterLabs’ x402 APIs answer unpaid calls with a real 402 challenge and settle in USDC on Base. Start at the x402 payment protocol page.
TRUTH FIRST. PROOF ALWAYS. — ScriptMasterLabs